If secession or expulsion ends in a "velvet divorce," as with Czechoslovakia, costs are
minimal and the split is relatively unimportant. High costs arise if a federation splits into mutually
hostile, comparably sized regions. Perhaps the majority of splits lead to dangerous hostility. A
well-designed constitution minimizes the likelihood of hostile splits by limiting the issues that are
dealt with at the federal level, by providing checks and balances, and by establishing due process
under the rule of law. Preventing the conditions under which a hostile split may arise is more costeffective
than trying to optimize the terms of a split or to find last-minute compromises to
forestall the split.

Because the conflicts that led to the American Revolution mainly arose from
constitutional issues, the history of these conflicts offers lessons for the design of the new
European Union constitution. One lesson is the importance of avoiding needless conflicts
between federal and member-state governments. In particular, forcing decisions on where
sovereignty lies may cause great conflict. Another lesson is that a federal system depends on
good will among the federal and member-state governments, and because this good will is easily
dissipated, efforts should be made to nurture it. Federal exercise of power will often alienate
member states; thus, a sensible strategy is to grant the federal government only the minimal
powers that a strong consensus agrees it must have, and to change these powers only by strong
consensus. Removing "democratic deficits" may not be sufficient in many cases to give
legitimacy to exercise of federal power; minorities may require protection by constitutional
limits on federal powers.